/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2008-2015 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 *
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.glassfish.grizzly.http.util;

import java.util.Date;

import java.text.DateFormat;
import java.text.FieldPosition;
import java.text.ParsePosition;

/**
 * Fast date formatter that caches recently formatted date information
 * and uses it to avoid too-frequent calls to the underlying
 * formatter.  Note: breaks fieldPosition param of format(Date,
 * StringBuffer, FieldPosition).  If you care about the field
 * position, call the underlying DateFormat directly.
 *
 * @author Stan Bailes
 * @author Alex Chaffee
 **/
public class FastDateFormat extends DateFormat {
    private static final long serialVersionUID = -1L;
    final DateFormat    df;
    long          lastSec = -1;
    final StringBuffer  sb      = new StringBuffer();
    final transient FieldPosition fp      = new FieldPosition(DateFormat.MILLISECOND_FIELD);

    public FastDateFormat(DateFormat df) {
        this.df = df;
    }

    public Date parse(String text, ParsePosition pos) {
        return df.parse(text, pos);
    }

    /**
     * Note: breaks functionality of fieldPosition param. Also:
     * there's a bug in SimpleDateFormat with "S" and "SS", use "SSS"
     * instead if you want a msec field.
     **/
    public StringBuffer format(Date date, StringBuffer toAppendTo,
                               FieldPosition fieldPosition) {
        long dt = date.getTime();
        long ds = dt / 1000;
        if (ds != lastSec) {
            sb.setLength(0);
            df.format(date, sb, fp);
            lastSec = ds;
        } else {
            // munge current msec into existing string
            int ms = (int)(dt % 1000);
            int pos = fp.getEndIndex();
            int begin = fp.getBeginIndex();
            if (pos > 0) {
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                ms /= 10;
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                ms /= 10;
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
            }
        }
        toAppendTo.append(sb.toString());
        return toAppendTo;
    }

    /**
     * Note: breaks functionality of fieldPosition param. Also:
     * there's a bug in SimpleDateFormat with "S" and "SS", use "SSS"
     * instead if you want a msec field.
     **/
    public StringBuilder format(Date date, StringBuilder toAppendTo,
                               FieldPosition fieldPosition) {
        long dt = date.getTime();
        long ds = dt / 1000;
        if (ds != lastSec) {
            sb.setLength(0);
            df.format(date, sb, fp);
            lastSec = ds;
        } else {
            // munge current msec into existing string
            int ms = (int)(dt % 1000);
            int pos = fp.getEndIndex();
            int begin = fp.getBeginIndex();
            if (pos > 0) {
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                ms /= 10;
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                ms /= 10;
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
            }
        }
        toAppendTo.append(sb.toString());
        return toAppendTo;
    }
    
//    public static void main(String[] args) {
//        String format = "yyyy-MM-dd HH:mm:ss.SSS";
//        if (args.length > 0)
//            format = args[0];
//        SimpleDateFormat sdf = new SimpleDateFormat(format);
//        FastDateFormat fdf = new FastDateFormat(sdf);
//        Date d = new Date();
//
//        d.setTime(1); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(20); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(500); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(543); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(999); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(1050); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(2543); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(12345); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(12340); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//
//        final int reps = 100000;
//        {
//            long start = System.currentTimeMillis();
//            for (int i = 0; i < reps; i++) {
//                d.setTime(System.currentTimeMillis());
//                fdf.format(d);
//            }
//            long elap = System.currentTimeMillis() - start;
//            System.out.println("fast: " + elap + " elapsed");
//            System.out.println(fdf.format(d));
//        }
//        {
//            long start = System.currentTimeMillis();
//            for (int i = 0; i < reps; i++) {
//                d.setTime(System.currentTimeMillis());
//                sdf.format(d);
//            }
//            long elap = System.currentTimeMillis() - start;
//            System.out.println("slow: " + elap + " elapsed");
//            System.out.println(sdf.format(d));
//        }
//    }
}
